ISO Standard Sizes of Drawings, Text Sizes, Heights

The table below shows ISO Standard for Tracing/Paper used in Engineering Drawings.

Note that A1 size is made by cutting A0 size in half and similarly A2 is size is half of A1 size, A3 size is half A2 size, etc.

All ISO paper sizes have the same aspect ratio, one to the square root of 2, meaning that a document designed for any given size can be enlarged or reduced to any other size and will fit perfectly. Given this ease of changing sizes, it is of course common to copy or print a given document on different sizes of paper, especially within a series, e.g. a drawing on A3 may be enlarged to A2 or reduced to A4, or more commonly, A1 reduced to A2 or A3 for convenience site works.

Note also A0 is very large and least used for Civil & Structural Engineering Drawings mainly because they are hard to handle on site. Usually A0 is reserved for very large Site Plan or large Overall Plot Plan. A1 is preferred for Drawings, while A2 & A3 are preferred for Site Drawings. Since photocopying machines can common with A3, plotting (not reducing from A1) on A3 is becomming a preferred size for all purposes. A4 should only be used for specific small details for site works, and where transmission by fax is required.

As a general guideline, all drawing should be prepared on A1 sized tracing/paper, while printing can be made in A2 or A3 to suit site works. With this in mind, the complexities of detailing should be reduced or configured accordingly so that when A1 is reduced to A2 or A3, the details are still legible and not a bundle of spots and black lines. Use of plot scales & correct text size are important considerations to be decided early.

Internal Frame Sizes / Drawing Boundary Lines

Internal frame or boundary lines is up to the individual company standards. Most would prefer to maximise drawing space. The edges range from 15mm to 50mm depending on plotter/printer edge requirements. Generally 20mm is good with 30mm for left edge where binding is required.

With the use of A3 in most office printers (not large A1, A0 plotters) the margin for A3 papers can be decrease further depending on the printer settings, a 5-10 mm seems fine in most cases, giving more drawing space for A3 format.

Pen Sizes, Line Thickness, Text Sizes, Text Heights

Where technical pens are used, sizes are chosen so that one could add detail or drafting changes with a pen width changing by approximately a factor of the square root of 2. A full set of pens would have the following nib sizes: 0.13, 0.18, 0.25, 0.35, 0.5, 0.7, 1.0, 1.5, and 2.0 mm. Other technical pens sizes : 0.2, 0.3, 0.4mm

ISO Standards called for four pen widths and set a colour code for each: 0.25 (white), 0.35 (yellow), 0.5 (brown), 0.7 (blue); these nibs produced lines that related to various text character heights and the ISO paper sizes.

With the use of CAD and ease of plotting (as compared to manual drafting on tracing paper) editing on computers and replotting is an easy task. As such the use of colors corresponding to pen sizes are common.

A company would have it's own standard to suit itself and plotting requirements. The following (non-standard) sizes works well. Note that plotting in autocad is by Color. It is also recommended that limited colors be used in detailing and plotting be all in black.

* Text Width "1 or min 0.8"

Do note that it is not necessary to comply strictly to International Standards except for ISO Paper sizes. Whatever works well with your company is fine and should be continued. However, if you do a lot of International Projects, then using a "common" system makes collabotation easy. We will cover these Internation Standards & Collaboration later.

Use Common Text Style

With the use of CAD, you can choose any Text Style you like. However, it is recommended that you use common text style so drawings can be exchanged between different CAD systems. Common types such as RomanS, RomanC, RomanT, RomanD, and TXT works fine. Avoid complex text style unless it is purely for graphic and aesthetics reasons. Try to use One Type of text style throughtout your drawings, eg Romans.

For Text Width, the default is set at 1 but you can use 0.8 or 0.9 which gives a better shape when plotted, and also you are able to squeeze in more text.

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